The present invention relates to a power convertor outlined in the preamble of claim 1.
The present invention also relates to an integrated circuit comprising such a power convertor and to a telecommunication device such as a telephone or facsimile provided with such a power convertor.
Such a power convertor also known as switched mode power supply and applied in an IC and telephone is generally known. In particular it is known from EP-A-0 190 110 to implement an output voltage stabilised power convertor in an integrated circuit and to use it in a telecommunication device, such as a telephone, a facsimile, a modem or the like. The known power convertor is provided with a switching control device for interrupting supplied input power. These power convertors have the known ability to convert with a high efficiency the supplied input voltages and currents from one value to another value. Their ability is being used for converting line power on a line such as a telephone line to voltages and currents which can be used for feeding internal features in the integrated circuit, telephone circuit, as well as in the telephone itself.
Nowadays communication devices have additional line power consuming features such as handsfree, listening-in, on hook dialling features, a loudspeaker used as a buzzer etcetera. Each country posses different specific demands on the telephone line and on the communication devices connected thereto when it comes to allowable voltages, currents and input impedances under varies line conditions. Telephone requirements make it in combination with certain of those features impossible to comply with the line requirements imposed by local national telecommunication authorities. This holds in particular for requirements concerning quantities such as minimum allowable input impedance under various line conditions.
So known power convertors have the disadvantage of not being able to hold line input quantities of such telecommunication devices within the prescribed boundaries under severe line/load conditions.